1 // SPDX-License-Identifier: GPL-2.0 2 #include <linux/fanotify.h> 3 #include <linux/fdtable.h> 4 #include <linux/fsnotify_backend.h> 5 #include <linux/init.h> 6 #include <linux/jiffies.h> 7 #include <linux/kernel.h> /* UINT_MAX */ 8 #include <linux/mount.h> 9 #include <linux/sched.h> 10 #include <linux/sched/user.h> 11 #include <linux/sched/signal.h> 12 #include <linux/types.h> 13 #include <linux/wait.h> 14 #include <linux/audit.h> 15 #include <linux/sched/mm.h> 16 17 #include "fanotify.h" 18 19 static bool should_merge(struct fsnotify_event *old_fsn, 20 struct fsnotify_event *new_fsn) 21 { 22 struct fanotify_event_info *old, *new; 23 24 pr_debug("%s: old=%p new=%p\n", __func__, old_fsn, new_fsn); 25 old = FANOTIFY_E(old_fsn); 26 new = FANOTIFY_E(new_fsn); 27 28 if (old_fsn->inode == new_fsn->inode && old->pid == new->pid && 29 old->path.mnt == new->path.mnt && 30 old->path.dentry == new->path.dentry) 31 return true; 32 return false; 33 } 34 35 /* and the list better be locked by something too! */ 36 static int fanotify_merge(struct list_head *list, struct fsnotify_event *event) 37 { 38 struct fsnotify_event *test_event; 39 40 pr_debug("%s: list=%p event=%p\n", __func__, list, event); 41 42 /* 43 * Don't merge a permission event with any other event so that we know 44 * the event structure we have created in fanotify_handle_event() is the 45 * one we should check for permission response. 46 */ 47 if (fanotify_is_perm_event(event->mask)) 48 return 0; 49 50 list_for_each_entry_reverse(test_event, list, list) { 51 if (should_merge(test_event, event)) { 52 test_event->mask |= event->mask; 53 return 1; 54 } 55 } 56 57 return 0; 58 } 59 60 static int fanotify_get_response(struct fsnotify_group *group, 61 struct fanotify_perm_event_info *event, 62 struct fsnotify_iter_info *iter_info) 63 { 64 int ret; 65 66 pr_debug("%s: group=%p event=%p\n", __func__, group, event); 67 68 wait_event(group->fanotify_data.access_waitq, event->response); 69 70 /* userspace responded, convert to something usable */ 71 switch (event->response & ~FAN_AUDIT) { 72 case FAN_ALLOW: 73 ret = 0; 74 break; 75 case FAN_DENY: 76 default: 77 ret = -EPERM; 78 } 79 80 /* Check if the response should be audited */ 81 if (event->response & FAN_AUDIT) 82 audit_fanotify(event->response & ~FAN_AUDIT); 83 84 event->response = 0; 85 86 pr_debug("%s: group=%p event=%p about to return ret=%d\n", __func__, 87 group, event, ret); 88 89 return ret; 90 } 91 92 static bool fanotify_should_send_event(struct fsnotify_iter_info *iter_info, 93 u32 event_mask, const void *data, 94 int data_type) 95 { 96 __u32 marks_mask = 0, marks_ignored_mask = 0; 97 const struct path *path = data; 98 struct fsnotify_mark *mark; 99 int type; 100 101 pr_debug("%s: report_mask=%x mask=%x data=%p data_type=%d\n", 102 __func__, iter_info->report_mask, event_mask, data, data_type); 103 104 /* if we don't have enough info to send an event to userspace say no */ 105 if (data_type != FSNOTIFY_EVENT_PATH) 106 return false; 107 108 /* sorry, fanotify only gives a damn about files and dirs */ 109 if (!d_is_reg(path->dentry) && 110 !d_can_lookup(path->dentry)) 111 return false; 112 113 fsnotify_foreach_obj_type(type) { 114 if (!fsnotify_iter_should_report_type(iter_info, type)) 115 continue; 116 mark = iter_info->marks[type]; 117 /* 118 * if the event is for a child and this inode doesn't care about 119 * events on the child, don't send it! 120 */ 121 if (type == FSNOTIFY_OBJ_TYPE_INODE && 122 (event_mask & FS_EVENT_ON_CHILD) && 123 !(mark->mask & FS_EVENT_ON_CHILD)) 124 continue; 125 126 marks_mask |= mark->mask; 127 marks_ignored_mask |= mark->ignored_mask; 128 } 129 130 if (d_is_dir(path->dentry) && 131 !(marks_mask & FS_ISDIR & ~marks_ignored_mask)) 132 return false; 133 134 if (event_mask & FANOTIFY_OUTGOING_EVENTS & 135 marks_mask & ~marks_ignored_mask) 136 return true; 137 138 return false; 139 } 140 141 struct fanotify_event_info *fanotify_alloc_event(struct fsnotify_group *group, 142 struct inode *inode, u32 mask, 143 const struct path *path) 144 { 145 struct fanotify_event_info *event = NULL; 146 gfp_t gfp = GFP_KERNEL_ACCOUNT; 147 148 /* 149 * For queues with unlimited length lost events are not expected and 150 * can possibly have security implications. Avoid losing events when 151 * memory is short. 152 */ 153 if (group->max_events == UINT_MAX) 154 gfp |= __GFP_NOFAIL; 155 156 /* Whoever is interested in the event, pays for the allocation. */ 157 memalloc_use_memcg(group->memcg); 158 159 if (fanotify_is_perm_event(mask)) { 160 struct fanotify_perm_event_info *pevent; 161 162 pevent = kmem_cache_alloc(fanotify_perm_event_cachep, gfp); 163 if (!pevent) 164 goto out; 165 event = &pevent->fae; 166 pevent->response = 0; 167 goto init; 168 } 169 event = kmem_cache_alloc(fanotify_event_cachep, gfp); 170 if (!event) 171 goto out; 172 init: __maybe_unused 173 fsnotify_init_event(&event->fse, inode, mask); 174 if (FAN_GROUP_FLAG(group, FAN_REPORT_TID)) 175 event->pid = get_pid(task_pid(current)); 176 else 177 event->pid = get_pid(task_tgid(current)); 178 if (path) { 179 event->path = *path; 180 path_get(&event->path); 181 } else { 182 event->path.mnt = NULL; 183 event->path.dentry = NULL; 184 } 185 out: 186 memalloc_unuse_memcg(); 187 return event; 188 } 189 190 static int fanotify_handle_event(struct fsnotify_group *group, 191 struct inode *inode, 192 u32 mask, const void *data, int data_type, 193 const unsigned char *file_name, u32 cookie, 194 struct fsnotify_iter_info *iter_info) 195 { 196 int ret = 0; 197 struct fanotify_event_info *event; 198 struct fsnotify_event *fsn_event; 199 200 BUILD_BUG_ON(FAN_ACCESS != FS_ACCESS); 201 BUILD_BUG_ON(FAN_MODIFY != FS_MODIFY); 202 BUILD_BUG_ON(FAN_CLOSE_NOWRITE != FS_CLOSE_NOWRITE); 203 BUILD_BUG_ON(FAN_CLOSE_WRITE != FS_CLOSE_WRITE); 204 BUILD_BUG_ON(FAN_OPEN != FS_OPEN); 205 BUILD_BUG_ON(FAN_EVENT_ON_CHILD != FS_EVENT_ON_CHILD); 206 BUILD_BUG_ON(FAN_Q_OVERFLOW != FS_Q_OVERFLOW); 207 BUILD_BUG_ON(FAN_OPEN_PERM != FS_OPEN_PERM); 208 BUILD_BUG_ON(FAN_ACCESS_PERM != FS_ACCESS_PERM); 209 BUILD_BUG_ON(FAN_ONDIR != FS_ISDIR); 210 211 BUILD_BUG_ON(HWEIGHT32(ALL_FANOTIFY_EVENT_BITS) != 10); 212 213 if (!fanotify_should_send_event(iter_info, mask, data, data_type)) 214 return 0; 215 216 pr_debug("%s: group=%p inode=%p mask=%x\n", __func__, group, inode, 217 mask); 218 219 if (fanotify_is_perm_event(mask)) { 220 /* 221 * fsnotify_prepare_user_wait() fails if we race with mark 222 * deletion. Just let the operation pass in that case. 223 */ 224 if (!fsnotify_prepare_user_wait(iter_info)) 225 return 0; 226 } 227 228 event = fanotify_alloc_event(group, inode, mask, data); 229 ret = -ENOMEM; 230 if (unlikely(!event)) { 231 /* 232 * We don't queue overflow events for permission events as 233 * there the access is denied and so no event is in fact lost. 234 */ 235 if (!fanotify_is_perm_event(mask)) 236 fsnotify_queue_overflow(group); 237 goto finish; 238 } 239 240 fsn_event = &event->fse; 241 ret = fsnotify_add_event(group, fsn_event, fanotify_merge); 242 if (ret) { 243 /* Permission events shouldn't be merged */ 244 BUG_ON(ret == 1 && mask & FANOTIFY_PERM_EVENTS); 245 /* Our event wasn't used in the end. Free it. */ 246 fsnotify_destroy_event(group, fsn_event); 247 248 ret = 0; 249 } else if (fanotify_is_perm_event(mask)) { 250 ret = fanotify_get_response(group, FANOTIFY_PE(fsn_event), 251 iter_info); 252 fsnotify_destroy_event(group, fsn_event); 253 } 254 finish: 255 if (fanotify_is_perm_event(mask)) 256 fsnotify_finish_user_wait(iter_info); 257 258 return ret; 259 } 260 261 static void fanotify_free_group_priv(struct fsnotify_group *group) 262 { 263 struct user_struct *user; 264 265 user = group->fanotify_data.user; 266 atomic_dec(&user->fanotify_listeners); 267 free_uid(user); 268 } 269 270 static void fanotify_free_event(struct fsnotify_event *fsn_event) 271 { 272 struct fanotify_event_info *event; 273 274 event = FANOTIFY_E(fsn_event); 275 path_put(&event->path); 276 put_pid(event->pid); 277 if (fanotify_is_perm_event(fsn_event->mask)) { 278 kmem_cache_free(fanotify_perm_event_cachep, 279 FANOTIFY_PE(fsn_event)); 280 return; 281 } 282 kmem_cache_free(fanotify_event_cachep, event); 283 } 284 285 static void fanotify_free_mark(struct fsnotify_mark *fsn_mark) 286 { 287 kmem_cache_free(fanotify_mark_cache, fsn_mark); 288 } 289 290 const struct fsnotify_ops fanotify_fsnotify_ops = { 291 .handle_event = fanotify_handle_event, 292 .free_group_priv = fanotify_free_group_priv, 293 .free_event = fanotify_free_event, 294 .free_mark = fanotify_free_mark, 295 }; 296